First off I have an '07 Outback with a dual battery setup and perko switch. I have listened to all the speakers in the boat and do not hear the high pitch noise threw them.

For tower speakers I have a set of Infinity's with the Infinity amp. These are the speakers I can hear the high pitch noise through. It goes away when the key is off, but soon as its on the noise starts. It gets annoying when just cruising around the lake.

I looked for a previous post for this but couldn't find it, any ideas to fix this?